I recently heard a presentation on this subject given by Marian Smith to the JGSSN (JGS of Southern Nevada) via Zoom. She is retired after 30 years working for the USCIS. Perhaps you can contact the group or go to their website and see if you can contact her directly. There was a handout along with the presentation that shows which records can be found at the various locations for such records, depending on when the immigration was and when the paperwork to become a US citizen was filed. Good luck to you.
Myrna (Slatnick) Waters
Researching: SLEPACK (or similar)Belarus/Bialystok area; SLATNICK/SLOTNIK (or similar) Minsk/Puchovichi area of Russia from 1905/1914 to NY & Newark,NJ and Canada; KURZMANN Jaslo, Poland and Drohobych, Ukraine area (both formerly in what was the Galician area of Austria prior to WWI), KURTZMAN in NY/Bronx and NJ/Newark from 1905/1910, SADOWSKY (or similar) from Belarus area of Russia/Bialystok 19th century to Newark,NJ 1905 or after.